Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Exp Gerontol. 2011 Sep;46(9):739-46. doi: 10.1016/j.exger.2011.05.004. Epub 2011 May 15.
Presbycusis, as the deterioration of hearing ability occurring with aging, can be manifested not only in a shift of hearing thresholds, but also in a deterioration of the temporal processing of acoustical signals, which may in elderly people result in degraded speech comprehension. In this study we assessed the age-related changes in the temporal processing of acoustical signals in the auditory system of pigmented rats (Long Evans strain). The temporal resolution was investigated in young adult (3-4 months) and old (30-34 months) rats by behavioral and electrophysiological methods: the rats' ability to detect and discriminate gaps in a continuous noise was examined behaviorally, and the amplitude-rate function was assessed for the middle latency response (MLR) to clicks. A worsening of the temporal resolution with aging was observed in the results of all tests. The values of the gap detection threshold (GDT) and the gap duration difference limen (GDDL) in old rats increased about two-fold in comparison with young adult rats. The MLR to a click train in old rats exhibited a significantly faster reduction in amplitude with an increasing stimulation rate in comparison with young adult rats. None of the age-related changes in the parameters characterizing temporal resolution (GDT, GDDL and MLR to a click train) correlated with the degree of the age-related hearing loss. However, the age-related changes in MLR amplitude-rate function correlated with the age-related changes in GDDL, but not with the changes in GDT. The behavioral and electrophysiological data clearly show that aging in rats is accompanied with a pronounced deficit in the temporal processing of acoustical signals that is associated with the deteriorated function of the central auditory system.
老年性聋是指随着年龄的增长而出现的听力能力下降，不仅表现在听力阈值的转移，还表现在听觉信号的时间处理能力下降，这可能导致老年人言语理解能力下降。在这项研究中，我们评估了色素沉着大鼠（Long Evans 品系）听觉系统中声音信号时间处理的与年龄相关的变化。通过行为和电生理方法研究了年轻成年（3-4 个月）和老年（30-34 个月）大鼠的时间分辨率：通过行为检查大鼠检测和区分连续噪声中间隙的能力，并评估了中间潜伏期反应（MLR）对点击的幅度-频率函数。所有测试的结果均表明，随着年龄的增长，时间分辨率变差。老年大鼠的间隙检测阈值（GDT）和间隙持续时间差阈（GDDL）值与年轻成年大鼠相比增加了约两倍。与年轻成年大鼠相比，老年大鼠对点击序列的 MLR 幅度随刺激率的增加而显著更快地降低。表征时间分辨率的参数（GDT、GDDL 和 MLR 对点击序列）的任何与年龄相关的变化均与与年龄相关的听力损失程度无关。然而，MLR 幅度-频率函数的年龄相关变化与 GDDL 的年龄相关变化相关，但与 GDT 的变化无关。行为和电生理数据清楚地表明，大鼠的衰老伴随着听觉信号时间处理能力的明显缺陷，这与中枢听觉系统功能恶化有关。
